The present invention relates to medical devices for closure of a severed sternum. In particular, the invention is directed to a sternum closure assemblies and methods for re-approximating split portions of tissue to retain the split portions in adjacent contacting relation to promote healing thereof.
During surgery that involves a median sternotomy, for example, open-heart surgery, the sternum is cut longitudinally to allow access to the organs within the thoracic cavity. A partial or median sternotomy is a procedure by which a saw or other comparable cutting instrument is used to make a midline, longitudinal incision along a portion or the entire axial length of the patient""s sternum, allowing two opposing sternal valves to be separated laterally. Upon completion of the surgery, the sternum is rejoined and closed securely.
Traditionally, the sternal halves have been closed with stainless steel wires which are wrapped around or through the sternal halves to engage in face-to-face relationship and compressed together while the sternum heals. For example, in one version, a surgical needle with the metal wire is led via both severed parts of a severed sternum and the free metal wire is cut-off. In another version, the wire tips are further led via openings in special staples, to project outside and the tips are twisted together by tightening the suture, U.S. Pat. No. 4,512,346 and U.S. Pat. No. 5,849,012. However, these devices have certain shortcomings, in that they require significant force, are difficult to maneuver and the sharp wire edges sometimes cause injury and eventually, infection to soft tissues.
Other prior art sternum closure assemblies include one or two metal plates, these plates being provided with rows of openings, through which extend the screws, pins, or metal wire, to bring together the severed parts of the sternum. U.S. Pat. No. 4,585,341. These devices have drawbacks in that they are ineffective in fixing the split parts of the severed sternum. Moreover, they are foreign bodies in the thoracic cavity, and they can cause disturbance in blood supply to the osseous tissue, thereby prolonging healing and increasing chances of infection.
The strap assemblies known heretofore incorporate clamps, clasps, bands, strips with or without openings and complex locking mechanisms. U.S. Pat. No. 5,356,417; U.S. Pat. No. 5,462,542; and U.S. Pat. No. 6,007,538. The use of compression prevents problems for blood circulation and soft tissues. Other versions of sternum closure devices use tongs, plugs or guns with anvils, to apply staples through the osseous tissue of the sternum. U.S. Pat. No. 4,122,989; and U.S. Pat. No. 4,481,960. However, these devices suffer from several drawbacks, for example, significant force is required to puncture the osseous tissue and insert a staple. In addition, these prior art devices are imprecise in positioning the staples, and do not permit the anvil to bend the staple through 180xc2x0 angle. Finally, the devices are cumbersome and cause shaking of the organs in the thoraxic cavity.
A certain amount of emphasis has also been directed towards the use of appropriate staples which minimize healing time, minimize distortion of the material stapled, minimize damage of material stapled, minimize scar tissue formation and achieve uniform compression of stapled material. U.S. Pat. No. 5,342,396 and U.S. Pat. No. 5,667,527. However, these devices suffer from several of the same drawbacks discussed above for earlier models of the sternum closure devices and systems.
It would accordingly be desirable to provide a sternum closure device which is stable in construction and effectively secures the severed parts of sternum or other tissue together, i.e., secures the staples in well defined locations, at a predetermined angle, and at a desirable tension to promote uniform healing of the tissue portions while avoiding complications associated with tissue injury, infection and compression.
The present invention provides improved devices and methods of joining with staples, the opposite parts of a severed sternum following a median or partial sternotomy that overcomes the above cited problems inherent in previous sternum closure devices. Generally, the present invention is embodied in an anvil for forming the staples, a bracket positioned opposite the anvil, a means for making openings in the tissue, and a mechanisms for feeding and mounting the staples.
According to a first aspect of the invention, a sternum closure device comprises an anvil having an element comprising two slots, said element being used for forming or shaping the staples. A bracket is provided with an additional slot to guide the drilling means and to mount the staples in the sternum. Other improvements to the anvil and bracket include forming elements which facilitate their mounting on the sternum parts. The bracket is provided with a post and a lock, the post having two mutually perpendicular openings and a pin mounted on it, and the lock comprising a housing with a slot, and a spring-actuated locking element with a handle situated in the slot.
According to a second aspect of the invention, the bracket is joined with the anvil through a spring-actuated screw having a handle, said screw being positioned in a threaded opening located in the bracket. Two guides are situated between the anvil and the bracket and parallel to the screw, said guides being installed in the openings of the bracket to facilitate displacement of the bracket with respect to the anvil.
The sternum closure device of the present invention comprises a bit brace with a reducing gear and two chucks having interchangeable drills for simultaneously drilling openings in both parts of a severed sternum. The reducing gear includes a housing, said housing including a basis with a lug, and a cover. The lug is provided with an opening and a slot. A driving gear wheel is installed on a driving shaft, said driving shaft being joined with a pneumatic drive. Two driven gear wheels are in engagement with the drive wheel gear. The driving wheel is fastened on the driving shafts, and chucks with interchangeable drills are installed on these driven shafts.
According to another aspect of the invention, the sternum closure device comprises a mechanism for feeding and mounting the staples, including a carrying element constructed of a bed, said bed having a first and second surface. Two ribs provided with a positive stopper are situated perpendicularly to the bed surface. The bed surface and each rib are provided with slots. The first bed surface is also provided with a lug having a threaded opening and a locking screw. The second and opposite bed surface is designed as a wall having a handle. A sub-assembly used for mounting the staples, is installed on the bed surface, said sub-assembly comprising an L-shaped lever and two spring-actuated posts. Said L-shaped lever has a shaft side and a long side. The two spring-actuated posts are locked on the bed surface and passed through the openings in the shaft side of the L-shape lever. The long side of the L-shaped lever is placed in the slot of the bed surface.
A cartridge is placed between the bed ribs, said ribs having an internal sand an external side. The cartridge comprises slots for the staples and a sprelement situated between the cartridge and the face wall of the bed. The spring-wise element presses the cartridge with staples against a plurality of stoppers installed on the internal side of the bed ribs.
According to a preferred embodiment of the invention, an instrument for drilling openings is installed on the bracket post along with precise and well-controlled mechanism or means for feeding and mounting staples. A compression spring is situated between the instrument for drilling openings and the mechanism or means for feeding and mounting staples. The instrument for drilling opening may be displaced from the bracket post when necessary.